Geology 141 (A): Fall, 2006 Second Hour Examination ... Page 14 ...
Geology 141(A) Name
Autumn, 2006 10 November, 2006
GE141: Understanding Earth ~
Second Hour Examination
INSTRUCTIONS: PLEASE read the instructions and questions CAREFULLY and completely. If you do not understand a question as it appears on the exam, PLEASE ASK FOR CLARIFICATION!! It is to YOUR benefit to do so. This examination is worth 175 points, or 17.5% of your overall semester grade. Exams will be graded as quickly as possible; your individual point total will be entered on the last page to ensure that only you know how well you did on the exam, unless you choose to divulge that information to others.
"Those who can make you believe absurdities can make
you commit atrocities." - Voltaire
Section I: Multiple-choice. Please circle the letter of the correct or best response to each question. Each question is worth 3 points; the section as a whole is worth 105 points of the 175 for the exam.
1. The elements above iron in the Periodic Table (the transferric elements) are considered evidence that our solar system, including the Earth, are a second-generation star system because these elements
a. must have come from outside our galaxy.
b. only form by radioactive decay deep underground.
c. are formed from cosmic rays bombarding the Earth.
d. form only in the extreme temperatures and pressures of exploding stars
(supernovas).
2. The two most abundant elements, by weight, in the Earth's crust are
a. iron and nickel c. oxygen and silicon
b. iron and silicon d. silicon and aluminum
3. The major mineral groups are classified according to
a. the density of the minerals c. the crystal structure of the minerals
b. the color of the minerals d. the chemical composition of the minerals
4. The only non-silicate mineral group that is more important for its abundance in the Crust than its economic significance is the
a. oxides c. carbonates
b. sulfides d. feldspars
5. Which of the following active volcanoes is NOT part of the Pacific Ring of Fire?
a. Mount St. Helens, Washington c. Tungurahua, Ecuador
b. Mauna Loa, Hawai'i d. Mt. Mayon, Philippines
6. What rock type would you most expect to find in a typical stratovolcano, such as the Soufriere Hills volcano on Montserrat, Tungurahua in Ecuador, or Mt. St. Helens in Washington State?
a. basalt c. andesite
b. gabbro d. granite
7. The minerals that comprise Bowen's Reaction Series are arranged, from top to bottom, by
a. their melting temperature (highàlow) and silica content (lowàhigh)
b. their position in the Palisades sill - those being higher in the sill being
placed higher in the diagram.
c. age of the minerals - those at the top date from earlier in Earth's history,
while those at the bottom are forming today.
d. their chemical composition - those at the top being non-silicates, while
those at the bottom are all silicates.
8. Typical island-arc systems include all of the following except
a. the Japanese archipelago c. the Kuril Islands
b. the Aleutian Islands d. the Hawaiian Islands
9. Biogenic sedimentary rocks are those derived at least mostly from the remains of organisms. Which of the following is NOT typically a biogenic sedimentary rock?
a. shale c. chert
b. limestone d. coal
10. ALL clays are ultimately derived from
a. fine-grained sediments formed by grinding of rocks.
b. mechanical weathering of non-silicate minerals.
c. chemical combinations of phosphate and carbonate minerals.
d. chemical weathering of silicate minerals.
11. The cartoon below shows a profile of a mountain outside a village in southern Mexico. You are part of an international eco-tourism group trying to develop an
economic base for the local people, based on the forests on the lower slopes of the mountain. What would be your initial assessment of this mountain, based on how it appears as an isolated, high peak, and where it is located?
a. It is likely comprised of basalt, and plants will have potassium deficiencies.
b. It is likely andesitic, since it is pretty clearly a stratovolcano.
c. It is likely uplifted sedimentary rock from the subduction along the Middle
America trench to the west.
d. It is impossible to even guess what it might be until you go take a look.
12. Potassium is extremely deficient in the soils in Hawai'i. Why would this be so?
a. the islands are entirely calcium carbonate, and have no potassium in
them.
b. the islands are entirely volcanic, and volcanic rocks never have potassium-
bearing minerals in them.
c. the islands are entirely basaltic, and basalts have very low potassium
content.
d. the constant rains in Hawai'i would weather any potassium to aluminum.
13.
14. A typical example of a sedimentary rock that normally contains no minerals is
a. andesite b. shale c. limestone d. conglomerate e. coal
15. A muddy sandstone is buried along the western margin of South America. Over time, it is pushed deeper and deeper into the crust. Temperatures rise, and eventually it melts. When this hardens and recrystallizes, what rock is going to be the most likely end product?
a. quartzite c. greenstone e. gneiss
b. granite d. schist
16. The only nutrient that plants need to get from the soils that does NOT come from the chemical weathering of minerals is
a. calcium d. magnesium
b. iron e. nitrogen
c. potassium f. sulfur
17. If Brucium were a radioactive isotope that had a half-life of 250 years, how much of 100 grams of Brucium would still exist after 1000 years?
a. none c. 6.25 grams e. you can't say
c. 50 grams d. 25 grams
18. AMS dating is used for
a. really old rocks, like those in the continental shields.
b. samples of organic matter too small for conventional radiocarbon dating.
c. samples of quartz exposed to cosmic rays.
d. direct age determinations on sedimentary rocks of any age.
19. While flying into San Francisco for a JanPlan internship, you look down from your plane and notice that the vineyards at a winery in the Napa Valley, and the road to the winery itself, have been offset as shown in the cartoon below.
What kind of fault is represented in this cartoon?
a. a normal fault d. an abnormal fault
b. a reverse fault e. a right-lateral fault
c. a left-lateral fault f. a transform fault
20. Most major mountain ranges in the world (the Appalachians, the Andes, the Himalaya, the Alps, the Urals, etc.) came into existence primarily as a result of what process?
a. erosion of surrounding rock that was once as high as they are.
b. convergence of lithospheric plates, resulting in folding and reverse faulting.
c. uplift of segments of the mid-oceanic rise and ridge system (MORRS)
caught up in ophiolite sequences.
d. volcanic continental arcs created by subduction zones along the coast.
21. The cartoon below illustrates a cross-sectional view of what kind of fault?
a. normal fault c. reverse fault e. transform fault
b. thrust fault d. drag fault f. strike-slip fault
22. What kind of stress would be most likely responsible for the kind of faulting depicted in question 20?
a. compressional stress c. torsional (twisting) stress
b. tensional stress d. shearing stress
23. The two processes most responsible for the long-term overall thickening
of continental crust are
a. deposition of sediments and volcanism
b. reverse faulting and folding of the rocks
c. intrusion of granites from magmas originating in the mantle.
d. the addition of organic matter from dead plants and animals.
24. An earthquake of magnitude 8 reflects about how much more ground shaking than an earthquake of magnitude 4?
a. about twice as much c. about 30 times as much
b. about 10 times as much d. about 10,000 times as much
25. The significance of S waves from earthquakes to our knowledge of the structure of the interior of the Earth is that they
a. reflect off the core back to the surface, so we can tell how thick the mantle
is.
b. are absorbed in the outer core, which indicates that it must be liquid.
c. create the earth's magnetic field in the solid inner core.
d. speed up through the core, so we know it must be partly solid.
26. The worst material upon which you can build a structure in an earthquake-prone region is
a. granite c. sandstone
b. artificial fill d. gneiss or slate
27. The seismic waves from earthquakes that do the most damage to cultural artifacts such as cities, highways, and buildings, are the
a. P-waves c. surface waves
b. S-waves d. reflected S-waves
28. While you were visiting the Grand Canyon this past summer, you saw a feature in the wall of a small side canyon that looked like the following sketch:
You now realize that what you saw was most likely a classic example of
a. a normal fault produced by tensional stress.
b. a reverse fault produced by compressional stress.
c. mass wasting in the form of a rotational slump.
d. a thrust fault created by mountain-building in a subduction zone.
29. The critical difference between mass wasting and faulting is that
a. mass wasting is caused by human actions, while faulting is natural.
b. mass wasting is driven by water, while faulting never involved water.
c. mass wasting is driven by gravity, while tectonics cause most faulting.
d. mass wasting only occurs at the Earth's surface, while faulting always
happens deep underground.
30. The importance of water in contributing to mass movements is that
a. it increases the mass on a slope.
b. it lubricates contacts between grains in the sediments or soils.
c. it pushes grains apart ("pore pressure").
d. it contributes to chemical and mechanical weathering, making earth
materials less able to resist gravity.
e. streams and waves (on an ocean or large lake) undercut slopes, making
them unstable.
f. all of the above.
31. Most sediments get into streams by
a. the stream downcutting through sediments and rocks.
b. chemical weathering of rocks within the stream bed.
c. mass wasting along the stream margins.
d. mechanical weathering of rocks within the stream bed.
e. wind blowing dry dust from upland areas down into the streams.
f. unknown processes that scientists are still trying to figure out.
32. The ultimate source for the water that begins the hydrologic cycle before it then falls as rain to become subsurface water and streams is
a. evaporation off the world's oceans.
b. condensation of steam from volcanic eruptions.
c. melting of glaciers and winter snows.
d. cosmic water from comets and extra-terrestrial sources.
33. What material is carried in the suspended load of a typical stream?
a. sand and gravel c. silts and clays
b. dissolved ions and organic matter d. salts, chemicals and pollutants
34. The sketch below depicts a segment of the hypothetical Whatsatooya River in
Alabama. What letter depicts areas where erosion will be the dominant geologic process?
A B C D E
35. Aquifer drawdown is caused by
a. pumping more water out of wells than is recharged into the system, on a
long-term (multi-year) basis.
b. water flowing out from the aquifers into streams.
c. water from the aquifers being withdrawn by plants in summer months.
d. water in the aquifers flowing downwards ever deeper into the Earth.
Section II: Please respond to each question in the most appropriate fashion. Please make your responses concise and to the point, but thorough; use sketch diagrams any place you believe that they may help explain your response. There should be ample space provided for an adequate response to each question; PLEASE RESTRICT YOUR RESPONSES TO THE SPACE PROVIDED. PLEASE ALSO try to write legibly; I CANNOT give any credit for responses I can't read! The number of points for each question is indicated in parentheses after the question; there are 70 points possible for this and the following section.
(And PLEASE remember as well that, as promised on the syllabus, I WILL deduct a point each time I see "volcanoe" or "techtonic!")
36. Identify five minerals that are found exclusively, or almost exclusively, in metamorphic rocks (5 points: 1 point each)
37. Identify two pairs of metallic cations that frequently and commonly will substitute for each other in silicate mineral structures. (5 points: 2-1-1-1)
often replaces
and
often replaces
38. The two principal gases in most magmas are (5 points: 3-2)
and
39. What is flocculation, and what is its significance for deposition of sediments in the ocean basins? (5 points)
40. The following two maps are of historical seismicity in areas that experienced earthquakes in the past two weeks. Why are these maps so different? What is going on, geologically, in each of these areas? (10 points)
(A) (B)
41. What can be dated accurately by each of the following two laboratory techniques, and over what age ranges are they appropriately applicable? (5 points total: 2-1-1-1)
40K - 40Ar
Materials
Age range
14C (radiocarbon)
Materials
Age range
42. The mass wasting process of heave results in a phenomenon called surface creep, which results in billions of dollars in damage annually to infrastructure (roads, buildings, retaining walls, etc.), both in the U.S. and abroad. Describe in detail how and why this process takes place, and feel free to use a sketch (or sketches) if it will help in your explanation. (10 points)
43. What are porosity and permeability as they relate to rocks or sediments, and what is their relationship to underground waters and aquifers? (5 points)
44. What is the water table, and what is the source of the true groundwater? (10 points)
Section III: Geography. On the maps on the following pages, please locate precisely each of the following localities or features. FOR SMALL FEATURES OR LOCALITIES, use a sharp arrow drawn from your label to the feature, so there can be no doubt about what you are labeling. PLEASE remember that IT IS TO YOUR BENEFIT that your label is clear enough that there is NO question as to your meaning or intent! (10 points, 1 point each)